Effects of Car Painting Vapors on Spirometric Parameters in Automobile Painting Workers

Background: Automobile spray painting is considered a high-risk occupation for respiratory diseases. The present survey aimed to assess the effects of automobile paint vapors on spirometric parameters among workers of a painting workshop in a large automobile manufacturing plant in Iran. Materials and Methods: This cross-sectional study was conducted on 820 workers of an automobile manufacturing plant, including 431 spray painters (case group) and 389 assembly line workers (control group). Spirometry was conducted for all participants under standard conditions, according to the American Thoracic Society (ATS) Clinical Practice Guidelines. The forced expiratory volume in one second (FEV1), forced vital capacity (FVC), FEV1/FVC, and forced expiratory flow at 25% and 75% of the pulmonary volume (FEF25-75) were reported. Results: Painters with more than ten years of work experience had significantly lower predicted values of FEV1/FVC (P= 0.005), FEV1 (P=0.008), and FEF25-75 (P=0.003), compared to the control group. Also, painters who were exposed to solvent-based paints were not significantly different from those exposed to water-based paints in terms of spirometric parameters (P>0.05). Conclusion: The results indicated the impact of automobile spray painting on the spirometric parameters. A slight decrease in the mean values of these parameters calls for attention to occupational safety, regular medical examinations, and effective measures.

as the concentration of paint vapor, formulation or composition of the paint (oil-based or water-based), and duration of exposure (9).
Overall, vehicle spray painters have shown lower pulmonary function indices (10,11). Despite the wellknown risks of exposure to diisocyanates, the manufacture and application of these compounds are still increasing (12). Monitoring of exposure to these chemicals during automobile body painting, implementing occupational hygiene and establishing medical surveillance programs (e.g., periodic PFTs for exposed workers) play essential roles in identifying the affected workers and decreasing the risk of respiratory disorders. Generally, PFTs are robust tests for detecting the effect of certain chemical exposures on the pulmonary function.
With this background in mind, in this study, we aimed to examine the potential effects of exposure to permissible levels of isocyanate on spirometric parameters in automobile body painters.

Study population
This analytical cross-sectional study consisted of 431 automobile spray painters aged 27-54 years (case group), as well as 389 workers in the same age group (control group), who were randomly selected from the assembly room of one of the largest automobile manufacturing plants in Iran. This study was conducted from March 2015 to November 2016. The exclusion criteria were as follows: 1) smoking; 2) respiratory disorders, such as pneumonia, asthma, and bronchitis; 3) consumption of respiratory drugs; and 4) exposure to other pollutants at home or in the workplace (Figure 1). Also, workers with less than five years of work experience were excluded from the study.
All participants were healthy with normal physical examination results.
A self-made questionnaire was used to extract the subjects' information regarding smoking habits, work experience, and the presence of diseases. The patients' height and weight were measured using standard instruments. The body mass index (BMI) was also calculated as weight/height 2 (kg/m 2 ). Painters were divided into two groups, based on exposure to solvent-or water-based paints. The Research Ethics Committee of Tehran University of Medical Sciences approved the study.

RESULTS
The study population consisted of 820 monoracial male workers, aged 27-54 years (mean: 36.73, SD: 3.70). No significant difference was observed regarding the mean age of exposed and non-exposed workers (36.73±2.98 vs. 36.74±4.36) (P=0.96). The mean work experience of exposed workers was significantly higher than that of non-exposed The results are demonstrated in Table 1.
The painters were classified into two groups, based on their work experience. Almost all spirometric parameters were lower in the exposed group with over ten years of work experience, compared to the non-exposed group.
There was a significant difference in terms of the mean predicted values of FEV1/FVC, FEV1, and FEF25-75 between the two groups (P<0.01). Moreover, painters with more than ten years of work experience were subsequently classified according to the exposure type (solvent-or water-based paints). However, considering the intergroup age difference, no significant difference was observed in the predicted values of FVC, FEV1, and FEF25-75 between painters exposed to solvent-based paints and those exposed to water-based paints. The results are shown in Table 2.  (14)(15)(16)(17)(18)(19). However, in the present study, no significant difference was found between the FVCs of the two study groups, which is not consistent with the findings of several studies (14,16,17).
Among workers with less than ten years of work experience, spray painters showed better results than the control group, although the difference was not statistically significant. This finding may be accidental or attributed to the recruitment of workers with healthier respiratory systems from the painting workshop and unhealthy workers from other sectors. The present results are in line with a previous study, which found no significant difference in FEV1 and FVC between exposed and nonexposed workers with less than five years of work experience (20). On the other hand, spirometric parameters, including FEV1, FVC, and FEF25-75, were significantly lower among exposed workers with over ten years of work experience, compared to non-exposed workers.
Despite the lack of a significant difference in the mean height, weight, and anthropometric indices of the two groups, a significant difference was observed in the mean age of the exposed and non-exposed groups.